The present disclosure relates to compounds, e.g., multisubstituted aromatic compounds, which exhibit biological activity, e.g., inhibitory action, against serine proteases, including thrombin and various kallikreins.
Kallikreins are a subgroup of serine proteases, divided into plasma kallikrein and tissue kallikreins. Plasma kallikrein (KLKB1) liberates kinins (bradykinin and kallidin) from the kininogens, peptides responsible for the regulation of blood pressure and activation of inflammation. In the contact activation pathway of the coagulation cascade, plasma kallikrein assists in the conversion of factor XII to factor XIIa (Keel, M.; Trentz, O. Injury 2005, 36, 691-709). Factor XIIa converts FXI into FXIa, which in turn activates FIX, which with its co-factor FVIIIa forms the tenase complex, which finally activates FX to FXa. In the fibrinolysis part of the coagulation cascade, plasma kallikrein serves to convert plasminogen to plasmin. Thus, it has been proposed that plasma kallikrein inhibitors can be useful in the treatment of thrombotic and fibrinolytic diseases and disease conditions (U.S. Pat. No. 7,625,944; Bird et al. Thrombosis and Hemostasis 2012, 107, 1141).
In rodent models, it has been shown that activation of plasma kallikrein in the eye increases retinal vascular permeability; whereas inhibition of the kallikrein-kinin system reduces retinal leakage induced by diabetes and hypertension. These findings suggest that intraocular activation of the plasma kallikrein pathway can contribute to excessive retinal vascular permeability that can lead to diabetic macular edema (DME). Thus, evidence suggests that plasma kallikrein inhibitors can provide a new therapeutic opportunity to reduce retinal vascular permeability (Feener, E. P. Curr Diab Rep 2010, 10, 270).
The Kallikrein-kinin system is involved in the regulation of vascular endothelial growth factor (VEGF), endothelial NO synthase, and fibroblast growth factor 2, all of which are involved in angiogenesis (Bader M. 2009, Arteriosclerosis, Thrombosis, and Vascular Biology, 29: 617). Tissue kallikrein (KLK1) has been linked to blood vessel growth (Miura S., 2003, Hypertension, 41, 1118). Therapies that moderate angiogenesis have been proposed for the treatment of both diabetic macular edema (DME) and age-related macular degeneration (AMD) (Syed, B. A.; Evans, J. B.; Bielory, L., 2012, Nature Reviews Drug Discovery, 11, 827). Without further wishing to be bound by any theory, it is therefore reasonable to conclude that KLK1 inhibitors can be useful in the treatment of diabetic retinopathy, DME, and AMD.
Studies have shown that inflammation plays an important role in the origin and development of AMD, and treatment often includes anti-inflammatories such as corticosteroid (Telander, D., 2011, Seminars in Ophthalmology, 26(3), 192). The connection between the kallikrein-kinin system and inflammation is also well established (Duchene, 2011, “Kallikrein-kinin system in inflammatory diseases”. Kinins. De Gruyter. 261). Without further wishing to be bound by any theory, it is reasonable to conclude that the anti-inflammatory nature of kallikrein (e.g. KLK1 and KLKB1) inhibitors can be useful in the treatment of AMD.
Ecallantide (Kalbitor) is a 60-amino acid recombinant protein that acts as a potent reversible inhibitor of plasma kallikrein (Schneider L, et al., J Allergy Clin Immunol 2007, 120, 416). Ecallantide has been approved by the FDA for the treatment of acute attacks of hereditary angioedema (HAE). Without further wishing to be bound by any theory, it is reasonable to believe that plasma kallikrein inhibition in general can be a useful treatment for HAE, and thus there is strong interest in the development of plasma kallikrein inhibitors as a therapy for HAE.
Tissue kallikreins (KLKs, for example, KLK1) are subdivided into various types, and have been extensively investigated in cancer and inflammation biology. Various kallikrein KLKs have been found to be up- or down-regulated in various cancer types, such as cervical-, testicular-, and non-small-cell lung adenocarcinoma (Caliendo et al. J. Med. Chem., 2012, 55, 6669). Furthermore, overexpression of various KLKs in the skin has led to the recognition that certain kallikrein inhibitors can be useful for certain dermatological conditions, including atopic dermatitis, psoriasis and rare skin diseases such as Netherton Syndrome (Freitas et al. Bioorganic & Medicinal Chemistry Letters 2012, 22, 6072-6075). A thorough discussion of tissue kallikrein, plasma kallikreins, their functions and potential roles in various diseases can be found in a variety of references, including the following which are incorporated herein by reference in their entireties and for all purposes: Renné, T.; Gruber, A. Thromb Haemost 2012, 107, 1012-3; Sotiropoulou, G.; Pampalakis, G. Trends in Pharmacological Sciences 2012, 33, 623-634; Pampalakis, G.; Sotiropoulou, G. Chapter 9 Pharmacological Targeting of Human Tissue Kallikrein-Related Peptidases. In Proteinases as Drug Targets, Dunn, B., Ed. The Royal Society of Chemistry: 2012; pp 199-228; Caliendo, G.; Santagada, V.; Perissutti, E.; Severino, B.; Fiorino, F.; Frecentese, F.; Juliano, L. J Med Chem 2012, 55, 6669-86.
In mammalian systems, blood vessel injuries result in bleeding events, which are dealt with by the blood coagulation cascade. The cascade includes the extrinsic and intrinsic pathways, involving the activation of at least 13 interconnected factors and a variety of co-factors and other regulatory proteins. Upon vascular injury, plasma factor VII interacts with exposed Tissue Factor (TF), and the resultant TF-fVIIa complex initiates a complex series of events. Factor fXa is produced directly ‘downstream’ from the TF-fVIIa complex, and amplified manifold via the intrinsic Pathway. FXa then serves as the catalyst for formation of thrombin (fIIa), which in turn is the direct precursor to fibrinolysis. The outcome is a fibrinolytic clot, which stops the bleeding. Fibrinolysis of the polymeric clot into fibrin monomers leads to dissolution and a return of the system to the pre-clot state. The cascade is a complex balance of factors and co-factors and is tightly regulated. In disease states, undesired up- or down-regulation of any factor leads to conditions such as bleeding or thrombosis. Historically, anticoagulants have been used in patients at risk of suffering from thrombotic complications, such as angina, stroke and heart attack. Warfarin has enjoyed dominance as a first-in-line anticoagulant therapeutic. Developed in the 1940s, it is a Vitamin K antagonist and inhibits factors II, VII, IX and X, amongst others. It is administered orally, but its ease of use is tempered by other effects: it has a very long half-life (>2 days) and has serious drug-drug interactions. Importantly, since Vitamin K is a ubiquitous cofactor within the coagulation cascade, antagonism results in the simultaneous inhibition of many clotting factors and thus can lead to significant bleeding complications.
Much attention has been focused on heparin, the naturally-occurring polysaccharide that activates AT III, the endogenous inhibitor of many of the factors in the coagulation cascade. The need for parenteral administration for the heparin-derived therapeutics, and the inconvenient requirements for close supervision for the orally available warfarin, has resulted in a drive to discover and develop orally available drugs with wide therapeutic windows for safety and efficacy. Indeed, the position of thrombin in the coagulation cascade has made it a popular target for drug discovery. Without wishing to be bound by any theory, it is believed that the ultimate development of direct thrombin inhibitors (DTIs) is usefully based upon the classical D-Phe-Pro-Arg motif, a sequence that mimics fibrinogen, which is a natural substrate of thrombin. Without further wishing to be bound by any theory, it is believed that the use of DTIs is very well precedented, such as with the hirudin-based anticoagulants, and thus there is strong interest in the discovery and development of novel DTIs.
A thorough discussion of thrombin and its roles in the coagulation process can be found in a variety of references, including the following which are incorporated herein by reference in their entireties and for all purposes: Wieland, H. A., et al., 2003, Curr Opin Investig Drugs, 4:264-71; Gross, P. L. & Weitz, J. I., 2008, Arterioscler Thromb Vasc Biol, 28:380-6; Hirsh, J., et al., 2005, Blood, 105:453-63; Prezelj, A., et al., 2007, Curr Pharm Des, 13:287-312.